<template>
    <div>
        <router-link tag='div' to='/' class="header-abs" v-show="showAbs">
            <div class="iconfont header-abs-back">&#xe682;</div>
        </router-link>
        <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
            <router-link to='/'>
                <div class="iconfont header-fixed-back">&#xe682;</div>
            </router-link>
            景点详情
        </div>
    </div>
</template>

<script>
import CommonGallary from 'common/gallary/Gallary'
export default {
    name: 'DetailHeader',
    data() {
        return {
            showAbs: true,
            opacityStyle: {
                opacity: 0
            }
        }
    },
    methods: {
        handleScroll(){
            // console.log('scroll')
            // console.log(document.documentElement.scrollTop)
            const top = document.documentElement.scrollTop
            if(top > 60){
                let opacity = top/140
                opacity = opacity > 1 ? 1 : opacity
                this.opacityStyle = {
                    opacity
                }
                this.showAbs = false
            }else{
                this.showAbs = true
            }
        }
    },
    // 当使用了keey-alive全局就可以使用activated方法
    activated() {
        /*
            调用了window不仅仅只在这个组件产生影响，还在全局组件也产生影响
        */ 
        // 用window调用监听事件    事件源      调用方法
        window.addEventListener('scroll', this.handleScroll)
    },
    // 什么时候开始执行：当页面即将被隐藏或者页面即将被新页面替换的时候
    deactivated() {
        window.removeEventListener('scroll', this.handleScroll)
    },
    
}
</script>

<style lang="stylus" scoped>
    @import '~styles/varibles.styl'
    .header-abs
        position absolute
        left .2rem
        top .2rem
        width .8rem
        height .8rem
        line-height .8rem
        border-radius .4rem
        background red
        text-align center
        .header-abs-back
            color white
            font-size .45rem
    .header-fixed
        z-index 2
        position fixed
        top 0
        left 0
        right 0
        height: $headerHeight;
        line-height: $headerHeight;
        text-align: center;
        color: #fff;
        background: $bgColor;
        font-size: .32rem
        .header-fixed-back
            position absolute
            top 0
            left 0
            width .64rem
            text-align center
            font-size .4rem
            color #fff
</style>